Recent in vitro studies have demonstrated that amyloid fibrils found in semen from healthy and HIV-infected men, as well as semen itself, can markedly enhance HIV infection rates. Semen fibrils are made up of multiple naturally occurring peptide fragments derived from semen. The best characterized of these fibrils are SEVI (semen-derived enhancer of viral infection), made up of residues 248 -286 of prostatic acidic phosphatase, and the SEM1 fibrils, made up of residues 86 -107 of semenogelin 1. A small molecule screen for antagonists of semen fibrils identified four compounds that lowered semen-mediated enhancement of HIV-1 infectivity. One of the four, gallic acid, was previously reported to antagonize other amyloids and to exert anti-inflammatory effects. To better understand the mechanism by which gallic acid modifies the properties of semen amyloids, we performed biophysical measurements (atomic force microscopy, electron microscopy, confocal microscopy, thioflavin T and Congo Red fluorescence assays, zeta potential measurements) and quantitative assays on the effects of gallic acid on semen-mediated enhancement of HIV infection and inflammation. Our results demonstrate that gallic acid binds to both SEVI and SEM1 fibrils and modifies their surface electrostatics to render them less cationic. In addition, gallic acid decreased semen-mediated enhancement of HIV infection but did not decrease the inflammatory response induced by semen. Together, these observations identify gallic acid as a non-polyanionic compound that inhibits semen-mediated enhancement of HIV infection and suggest the potential utility of incorporating gallic acid into a multicomponent microbicide targeting both the HIV virus and host components that promote viral infection.Amyloid fibrils are ordered protein aggregates associated with a large number of human diseases, many of which are neurodegenerative in nature, such as Alzheimer disease and Parkinson disease (1-3). They are characterized by their cross-␤ structure, with ␤ sheets running perpendicular to the fibril axis, and by their ability to bind to certain fluorescent dyes, such as thioflavin T (ThT), 4 whose fluorescence intensity increases considerably upon binding to amyloid fibrils.Amyloid fibrils are also found in semen from young, healthy men (4). Whether these fibrils serve a physiological function is not known, but they have been shown to markedly increase infection by a variety of sexually transmitted viruses, most notably HIV-1 (5-7). Under limiting dilution conditions, semen fibrils can increase HIV infection rates by up to 5 orders of magnitude (6). These fibrils are made up of naturally occurring peptide fragments in semen (6, 8 -10). The best characterized semen fibril is made up of a 39-residue fragment from human prostatic acid phosphatase (PAPf39) and has been termed SEVI (semen-derived enhancer of viral infection) (6). More recently, a second set of semen fibrils was identified from prostate-specific antigen-generated fragments of semenogelin (referred to collectivel...

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Green algae display a wide range of extracellular matrix (ECM) components that include various types of cell walls, scales, crystalline glycoprotein coverings, hydrophobic compounds and complex gels or mucilage. Recently, new information derived from genomic/transcriptomic screening, advanced biochemical analyses, immunocytochemical studies and ecophysiology has significantly enhanced and refined our understanding of the green algal ECM. In later diverging charophyte group of green algae, the cell wall and other ECM components provide insight into the evolution of plants and the ways the ECM modulates during environmental stress. Chlorophytes produce diverse ECM components, many of which have been exploited for various uses in medicine, food and the production of biofuels. This review highlights major advances in ECM studies of green algae.

One of the first steps in the origin of life was the formation of a membrane, a physical boundary that allowed the retention of molecules in concentrated solutions. The proto-membrane was likely formed by self-assembly of simple readily available amphiphiles, such as short-chain fatty acids and alcohols. In the commonly accepted scenario that life originated near hydrothermal systems, how these very simple membrane bilayers could be stable enough in time remains a debated issue. We used various complementary techniques such as dynamic light scattering, small angle neutron scattering, neutron spin-echo spectroscopy, and Fourier-transform infrared spectroscopy to explore the stability of a novel protomembrane system in which the insertion of alkanes in the midplane is proposed to shift membrane stability to higher temperatures, pH, and hydrostatic pressures. We show that, in absence of alkanes, protomembranes transition into lipid droplets when temperature increases; while in presence of alkanes, membranes persist for longer times in a concentration-dependent manner. Proto-membranes containing alkanes are stable at higher temperatures and for longer times, have a higher bending rigidity, and can revert more easily to their initial state upon temperature variations. Hence, the presence of membrane intercalating alkanes could explain how the first membranes could resist the harsh and changing environment of the hydrothermal systems. Furthermore, modulating the quantity of alkanes in the first membranes appears as a possible strategy to adapt the proto-membrane behavior according to temperature fluctuations, and it offers a first glimpse into the evolution of the first membranes.